Project 1: Time Domian Electron Paramagnetic Resonance Imaging:Summary:a) Instrumentation: We have developed instrumentation to with data acquisition modalities utilizing "Time-locked sub sampling" strategies. This modality uses low speed data acquisition ( 20 - 100 MHz) to sample high-speed transient data without loss of integrity of the signal quality. The advantage of this modality is that low-cost signal averagers with better dynamic range can be utilized in imaging. Specifically, in imaging experiments, the dynamic range of the image intensity will be significantly improved so that low intensity pixels will be validly represented even in the presence of high intensity regions.b) Digital EPR imaging spectrometer: Until now the EPR imaging instrumentation utilized spectrometers using analog modules. With the recent availability of digital signal processing technology (DSP), we have initiated the implementation of digital version of the EPR Imaging spectrometer. The specific advantages of this effort are that significant reduction in time of image data collection/reconstruction as well as elimination of noise contributions associated with analog components. We completed a test platform and successfully implemented a DSP based EPR imaging spectrometer.c) Graphic User Interface: Since the EPR Imaging spectrometer is an NIH built research spectrometer; the operation of the scanner is fairly complicated and also can be damaged by users unfamiliar with instrumentation. Since most in vivo experiments are carried out by members of the lab with minimal experience with instrumentation, we have developed a graphics user interface (GUI) to make the operation of the scanner for data collection user friendly as well as an additional interface for image reconstruction and display.